Processing and properties of natural fibers reinforced thermoplastic and thermosseting composites

In this work, three different natural fibers were studied and characterized, using optical and SEM microscopy. Woven fabrics of those reinforcement fibers were used to reinforce polyester and epoxy matrices and produce composite plates by vacum lay-up. Also, using an experimental piston blender equipment, long fiber reinforced PLA (LFT) composites were manufactured by hot compression molding. All different obtained composite plates were submitted to mechanical testing in order to determine relevant mechanical proprieties.Fundação para a Ciência e a Tecnologia (FCT

Processing and properties of composites obtained from natural fibres and thermosetting matrices

In this work, different natural fibres were studied and characterized, using optical and SEM microscopy. Those fibres were used to reinforce polyester and epoxy matrices and produce composite plates by hand lay-up. A vacuum bag was then used to allow improving the fibre impregnation, establishing a controlled pressure atmosphere. All different obtained composite plates were submitted to mechanical testing, in order to determine relevant mechanical proprieties. The produced composites were, namely, submitted to flexure and tensile tests, in accordance to ISO 14125 and ISO 527, standards, respectively. It was also determined, for each type of composite, the GIIc property (critical energy release rate in mode II), in order to assess their impact behaviour.Fundação para a Ciência e a Tecnologia (FCT

Development and assessment to environmentally friendly natural fiber composites

Two different types of natural fibers (jute and sisal) were studied and characterized, using optical microscopy, pycnometry density, single filament and linear density tests. Jute fibers were processed into composite parts from woven fabrics raw-material and sisal fibers were also processed into final composite componentes but in the form of chopped mat. Those fibers were used to reinforce polyester and epoxy matrices and therefore produce composite plates by resin infusion molding. Finally, the final obtained composite plates were submitted to mechanical testing, in order to assess their relevant mechanical properties.Fundação para a Ciência e a Tecnologia (FCT

A new hard-particle model for anisotropic fluids

We report a new hard-particle model system consisting of hard cylinders, we have determined the geometrical conditions that let us know whether or not two given cylinders overlap. In addition we have carried out Monte Carlo simulations sampling the canonical ensemble on this system, the numerical results indicate that this system exhibits mesomorphic behaviour

Radiación gama atmosférica de alta energía, a bajas latitudes

Se describe un experimento que midió el espectro de la radiación gama atmosférica a gran altura, con instrumental transportado por un globo estratosférico. El sistema detector utiliza, como componente principal, un centelleador plástico de gran volumen. Usando su función respuesta, que se ha calculado por separado (Azcárate y otros, 1975), se deduce que el espectro de pérdidas de energía observado a 5 g- cm⁻², es justificado por un flujo isotrópico, dado por la ley 0.34 E-1.1 fotones/cm 2 seg M eV. Esta expresión parece válida para rayos gama desde unos pocos M eV hasta, por lo menos, algunas decenas de M eV. El globo fue lanzado desde Paraná, Argentina, y su vuelo cubrió una región de baja latitud geo magnética.An experiment is described that measured the atmospheric gamma ray spectrum at balloom altitudes. The detector uses a large volume plastic scintillator as main component. By utilizing its response function, as computed separately (Azcárate et al, 1975), the observed energy losses distribution is accounted by an incident isotropie flux, at 5 g. cm-2 atmospheric depth, given by 0.34 E’ 1-1 photons/cm2 seg MeV. This expression appears valid for gamma rays from few MeV up, at least, some tens of MeV. The balloon was launched from Paraná, Argentina, and the measurement covers a region of low geomagnetic latitude.Asociación Argentina de Geofísicos y Geodesta

Radiación gama atmosférica de alta energía, a bajas latitudes

Se describe un experimento que midió el espectro de la radiación gama atmosférica a gran altura, con instrumental transportado por un globo estratosférico. El sistema detector utiliza, como componente principal, un centelleador plástico de gran volumen. Usando su función respuesta, que se ha calculado por separado (Azcárate y otros, 1975), se deduce que el espectro de pérdidas de energía observado a 5 g- cm⁻², es justificado por un flujo isotrópico, dado por la ley 0.34 E-1.1 fotones/cm 2 seg M eV. Esta expresión parece válida para rayos gama desde unos pocos M eV hasta, por lo menos, algunas decenas de M eV. El globo fue lanzado desde Paraná, Argentina, y su vuelo cubrió una región de baja latitud geo magnética.An experiment is described that measured the atmospheric gamma ray spectrum at balloom altitudes. The detector uses a large volume plastic scintillator as main component. By utilizing its response function, as computed separately (Azcárate et al, 1975), the observed energy losses distribution is accounted by an incident isotropie flux, at 5 g. cm-2 atmospheric depth, given by 0.34 E’ 1-1 photons/cm2 seg MeV. This expression appears valid for gamma rays from few MeV up, at least, some tens of MeV. The balloon was launched from Paraná, Argentina, and the measurement covers a region of low geomagnetic latitude.Asociación Argentina de Geofísicos y Geodesta

Discriminative capacity and construct validity of the Clock Drawing Test in Mild Cognitive Impairment and Alzheimer's disease

OBJECTIVES: The aim of this study was to analyze the psychometric and diagnostic properties of the Clock Drawing Test (CDT), scored according to the Babins, Rouleau, and Cahn scoring systems, for Mild Cognitive Impairment (MCI) and Alzheimer's disease (AD) screening, and develop corresponding cutoff scores. Additionally, we assessed the construct validity of the CDT through exploratory and confirmatory factor analysis. METHODS: We developed a cross-sectional study of ambulatory MCI and AD patients, divided in two clinical groups (450 MCI and 250 mild AD patients) and a normal control group (N = 400). All participants were assessed with the CDT, Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) for convergent validity. RESULTS: The selected scoring systems presented adequate validity and reliability values. The proposed cutoff scores showed 60 to 65% sensitivity and 58 to 62% specificity to identify MCI patients. The corresponding values for AD were 84 to 90% sensitivity and 76 to 78% specificity. Exploratory and confirmatory factor analysis revealed that the Babins scoring system had good construct validity and allowed us to propose a three-factor model for this system. CONCLUSIONS: Our results confirmed the complexity of the CDT and support it as a cognitive screening instrument particularly sensitive to AD. The use of the CDT with MCI patients should be interpreted with more caution due to the lower sensitivity and specificity for milder forms of cognitive impairment.info:eu-repo/semantics/publishedVersio

The broad iron Kalpha line of Cygnus X-1 as seen by XMM-Newton in the EPIC-pn modified timing mode

We present the analysis of the broadened, flourescent iron Kalpha line in simultaneous XMM-Newton and RXTE data from the black hole Cygnus X-1. The XMM-Newton data were taken in a modified version of the timing mode of the EPIC-pn camera. In this mode the lower energy threshold of the instrument is increased to 2.8 keV to avoid telemetry drop outs due to the brightness of the source, while at the same time preserving the signal-to-noise ratio in the Fe Kalpha band. We find that the best-fit spectrum consists of the sum of an exponentially cut off power-law and relativistically smeared, ionized reflection. The shape of the broadened Fe Kalpha feature is due to strong Compton broadening combined with relativistic broadening. Assuming a standard, thin accretion disk, the black hole is close to rotating maximally.Comment: Astron. Astrophys., in pres

Targeting Alzheimer’s disease with multimodal polypeptide-based nanoconjugates

Alzheimer’s disease (AD), the most prevalent form of dementia, remains incurable mainly due to our failings in the search for effective pharmacological strategies. Here, we describe the development of targeted multimodal polypeptide-based nanoconjugates as potential AD treatments. Treatment with polypeptide nanoconjugates bearing propargylamine moieties and bisdemethoxycurcumin or genistein afforded neuroprotection and displayed neurotrophic effects, as evidenced by an increase in dendritic density of pyramidal neurons in organotypic hippocampal culture. The additional conjugation of the Angiopep-2 targeting moiety enhanced nanoconjugate passage through the blood-brain barrier and modulated brain distribution with nanoconjugate accumulation in neurogenic areas, including the olfactory bulb. Nanoconjugate treatment effectively reduced neurotoxic amyloid aggregate levels and rescued impairments to olfactory memory and object recognition in APP/PS1 transgenic AD model mice. Overall, this study provides a description of a targeted multimodal polyglutamate-based nanoconjugate with neuroprotective and neurotrophic potential for AD treatment. Copyrigh